Technical Field
The instant disclosure relates to a capacitive sensing technique, in particular to a capacitance sensor device and detecting method for a conductive matter thereon.
Related Art
To enhance convenience in operation, more and more electronic devices are equipped with touch screens as the operating interface, such that a user can operate the device by directly touching the screen, thereby providing more convenient and friendly operating mode. The touch screen is primarily made of a displaying device having displaying capabilities and a sensing device providing touch-sensing capabilities.
Based on structural characteristics and sensing modes, sensing devices can be divided into the following categories: impedance sensing devices; capacitive sensing devices; acoustic sensing devices; optical (infrared), sensing devices; and electromagnetic sensing devices. In particular, sensing devices of capacity type do not need elastic material that reacts to external forces, are less responsive to ambient lighting condition, and have a simpler manufacturing process. Thus most current touch screens use capacitive sensing devices.
When the capacitive sensing device has an irregular conductive matter region (such as water or other conductive matter), the equivalent circuit and equivalent parasitic capacitance between the axial conductive lines in the region change accordingly. Consequently, the control sensing circuit picks up a change in the electrical current or charge transferred on the axial conductive lines, leading to false positives and false motion. In another scenario, if the touched point is in the irregular conductive matter region, the control sensing circuit detects a relatively smaller amount of electrical current or charge transfer for the axial conductive lines at the touched location. Additionally, due to the irregular conductive matter region, the conductive lines are connected to adjacent axial conductive lines (connected to ground via the adjacent axial conductive lines), thus rendering the control sensing circuit unable to identify the touched location correctly.
Therefore, how to effectively avoid false positives and wrong actions due to the irregular conductive matter(s) is one of the research goals undertaken by the industry.